The present invention relates to a swash plate type variable displacement compressor in which a plurality of pistons engaged with a swash plate reciprocate with a stroke length in accordance with an inclination angle of the swash plate.
Japanese Unexamined Patent Application Publication No. 1-190972 discloses a compressor of swash plate type having a movable body that is coupled to the swash plate and allows the swash plate to change its inclination angle. The movable body is movable in the axial direction of a rotary shaft of the compressor in response to a change in pressure of control gas (refrigerant gas) introduced into a control pressure chamber formed in a housing of the compressor. The inclination angle of the swash plate is varied by the movement of the movable body in the axial direction of the rotary shaft.
Specifically, when the pressure in the control pressure chamber is increased approximately to a level corresponding to the pressure of a discharge-pressure zone of the compressor, the movable body moves in the axial direction of the rotary shaft toward one end of the rotary shaft. With such movement of the movable body to the one end of the rotary shaft, the inclination angle of the swash plate is increased. When the pressure in the control pressure is decreased approximately to a level corresponding to the pressure of a suction-pressure zone of the compressor, on the other hand, the movable body moves in the axial direction of the rotary shaft toward the other end of the rotary shaft. With such movement of the movable body to the other end of the rotary shaft, the inclination angle of the swash plate is decreased. With a decrease in the inclination angle of the swash plate, the stroke length of the pistons and hence the displacement of the compressor are decreased. With an increase in the inclination angle of the swash plate, the stroke length of the pistons and hence the displacement of the compressor are increased. The swash plate type variable displacement compressor disclosed in the above-cited publication has a displacement control valve that controls the pressure in the control pressure chamber.
In such a swash plate type variable displacement compressor, a throttle is provided in a first supply passage at a midway position thereof between the discharge-pressure zone and the control pressure chamber. Such throttle restrains the flow of the control gas supplied from the discharge-pressure zone to the control pressure chamber through the first supply passage to thereby facilitate holding of the inclination angle of the swash plate at an intermediate position between the maximum and minimum inclination angle positions. Accordingly, the operating efficiency of the compressor at an intermediate displacement is improved.
However, the provision of such throttle in the first supply passage prevents the pressure in the control pressure chamber from being increased rapidly to a level corresponding to the pressure of the discharge-pressure zone when the air-conditioning switch of a vehicle air conditioner is turned ON to supply electric current to the electromagnetic solenoid and an instruction is made by a control computer for the operation of the compressor at the maximum displacement. As a result, the inclination angle of the swash plate cannot be changed to the maximum rapidly, thus taking a long time before the operation of the compressor at the maximum displacement is started.
The present invention has been made in view of the circumstances above and is directed to providing a swash plate type variable displacement compressor that changes the inclination angle of the swash plate to the maximum rapidly when electric current it supplied to the electromagnetic solenoid and the compressor is instructed to operate at the maximum displacement.